Roofing Services

Reflective Roofs…Do They REALLY Save Money?

In today’s energy conscious society, it’s imperative to be on the cutting edge of energy efficiency. With the introduction of cool roof systems including highly reflective thermoplastic, polyvinyl chloride, and other manufactured membranes, it’s tough to know how they all stack up. So, do these membranes live up to their reputation and actually lower your carbon footprint while saving you money at the same time? The answer, in our Midwest mixed weather climate, is no.

The reasons for loss of reflectance in single ply membranes were reasonably confirmed through this study (see link below) to be related to the growth of microorganisms on the surface of all the membranes. This fungal biomass is influenced by the number of rain days, average humidity, daily temperature change, and time. Throughout the life of the membrane, plasticizers used to keep the material from becoming brittle and tearing as well as some chemicals used to adhere the membrane migrate to the surface creating a tacky environment that encourages the growth of these biomasses and ultimately reduce the overall reflectance of the membrane. Over the course of a three year time period, reflectant membranes can lose 20%-50% of their original reflectance. Initial energy cost savings considering a roof insulation value of R-15 can be projected as roughly $0.13 ft2 in a cooling-dominated environment such as Phoenix, AZ and $0.00 ft2 in a mixed weather environment such as Omaha, NE. Washing the membrane with commercially available cleaners has been shown to restore much of the membrane’s reflectance, but actually washes away the chemicals that maintain the membrane’s physical integrity. In some circumstances, the membrane manufacturer will even void the warranty of the membrane if it is cleaned.

As you can see, choosing a reflective roof membrane in our Midwest mixed weather climate actually does not have any real energy cost benefits.